Low-heat-level evaporator system



1,623 941 Aprll. 5 1927.. L- E. SEBALD a LOW HEAT LEVEL EVAPQRATOR SYSTEM Filed Aug. 24, 1922 1 7a w Wafer 77/r/2ine Condcnsa (e earn awue/ntoz I 35% flbli'omm .r

M, UM, M1 W steam-for running auxiliary apparatus of system. a

' ratus from which the exhaust is returns.

Patented Apr. 5, 192 7.

UNITED STATES "PATENT, OFFICE-.7

LEsmE EARL SEBALD, or mneEwoon, NEW JERSEY, assrenon rornE Gaiseorr- EUssELL COMPANY, or NEW YORK, ,n. Y., A conronarron or DELAWARE.

LOW-HEAT-LEVEL EVAPORATOR SY STEM.

Application filed August 24, 1922. SerialNo. 583,977.

This invention relates to a combined evaporator and feed water system for supplying pure boiler feed in steam generating plants.

Where steam power is generated in quan-v tity as for example where large steam engines are used, the condensed steam from the engines is ordinarily returned to the boiler, the boilers and enginesforming acausing the water in the'open heater to boil closed circuit in which the water is repeatedly used. There are,, however, losses in this water incidental to the operation of the plant caused by leakage, by the use of such a character that this steam cannot be entirely returned to the system, and by the use of steam for heating water for industrial use. This loss is made up by the distilla'tion of raw water in order to prevent scale-forming or injurious impurlties .from being carried into the boilers.

'Ilhis additional or makeupl,Water is usually supplied to the boiler feed by evaporators which are heated by steam from the main boilers, and if the quantity of water to be made up reaches morethan a small percentage of the boiler capacity the heat losses incidental to vaporizing such a quantity of water will materially reduce the efiiciency of the power plant as a whole unless proper provision is made to return to the boilers the heat diverted, to the evaporator It has" heretofore been proposed to condense the vapor from the evaporators-in the main feed water heater for the 'boiler feed, thereby conserving the latent heat of vaporization, but in power plants utilizing high pressure steam and high pressure evaporators the condensed vapor from the evaporators and the condensed steam from the evaporator coils are at high temperature and hence contain a. large quantity of sensible heat which, if wasted, materially lowers the efliciency of the plant as a whole. To avoid this it has been proposed to deliver all the condensed vapor and steam from the evaporator and its coils and from. other applaa along with the condensed steam from the engines to a common open heater where the heat from the high pressure apparatus as well as the auxiliary exhaust steam is absorbed by the condensate from the main engines which is at a lower temperature In some instances this arrangement issatisabove the atmospheric boiling point, thus and entailing'loss ofa portion of the heat which should be given up to the boiler feed water. I 3 V Generally speaking it,is an object of the present invention to provide a combined evaporator and boiler feed system in which the resident heat of the system is efiiciently utilized, and at the same time the quantity of heat supplied to the open heater reduced to an amount which may be conveniently absorbed therein. g

It is a. further object of the invention to provide a system of the above type which is capable of furnishing a large percentage of makeup water without raising the tem- 'perature in the open heater above atmos-' pheric boiling point, and which is adapted to efliciently operate under various percentages of makeup and varying conditions of load.

More specifically it is an object of this invention to provide in a system of the above type an additional heat exchanger positioned between the plant open heater and the con-,

denser which accommodates the evaporator vapor output for the purpose of transferring heat to the boiler feed water at a tempera.- ture intermediate that of the. said condenser and the open heater, whereby the quantity of heat contained in the hot fluid discharged. into the open heater is reduced to an amount which can be absorbed without loss.

I have illustrated a preferred embodiment of my invention in the accompanying drawings, 'n which Fig. 1 is a view largely diagrammatic illustrating a power plant layout embodying my invention.

In Fig. 1 is shown a preferred system embodying my invention which is particularly designed for a plant requiring a relatively large quantityof boiler feed makeup water. A mult-i-efieet evaporator plant is s own in which the shell of each efi'ect is-eonnected with theheating coil of the succeeding effect, the vapor from the last effect being passed to a condenser 21. Drains from the eoils'5 of the several effects are passed through traps 7 to a common line 8, which line communicates by means of a branch line 19 with line 2 leading from the last efl'ect evaporator. Line 8 being in direct communication with the last evaporator effect is at the same pressure as exists in the shell of this effect, and consequently there will be a certain amount of flash steam available from the coil drains.

This flash steam passes through line 19, ad-

mitting of regulation by means of the valve hot condensate discharged through traps 22 and 23 is here utilized for heating the boiler feed in the same manner as has been described, the condensate from condenser 10 passing to the open heater. The boiler feed water passes in series through the open heater, the condenser 10, and the condenser 21, from whence it is conveyed to the boilers.

' It is to be understood that, if desired, the

condenser 10 may be'cut out of service by closing the valvell, in which case the drains from the" system are passed into the open heater by way of the by-pass 9 around trap 9. V v

I have referred to the heat exchanger 10 as a condenser, but it is apparent that this term is not to be construed as referring to a specific type of heat exchanger, but that any well known type of apparatus may be employed which is designed to efiect an exchange of heat between two fluid mediums.

While I have illustrated a preferred embodiment-of my invention various changes may be made inthe arrangement of the parts of the system and the invention is not restricted to any particular type of evaporators, condensers, or the like. Various changes may be madeiwithin the full scope of the appended claims.

I claim:

1. In a combined multi-efi'ect evaporator and boiler feed system, means for joining the drains from all the evaporator coils at substantially the pressure existing in the shell of the last efl ect evaporator, means for conveying the resulting flash steam from said drains together with vapor from thesaid evaporator shell to a condenser, said condenser being adapted to receive said joined vapors and transfer heat therefrom to the boiler feed water, means for joining the condensatefrom said coils with the condensate from said condenser at a pressure lower than that maintained in said condenser, a second condenser operating at saidv lower pressure for receiving said condensate and bringing it into heat exchangin g relation with the boiler feed water at said lower pressure, and means for conveying the condensate from said second condenser to the primary boiler feed heater, said boiler feed water passing successively through the primary heater, the second condenser and the first condenser.

' 2. In a combined multi-efi'ect evaporator and boiler feed heating system, means for conveying the vapor from an evaporator shell to a condenser, said condenser being adapted to receive said vapor and transfer heat therefrom to the holler feed water, means for joining the condensate from the evaporator coils with the condensate from said condenser, a second condenser operating at a lower pressure than that maintained in' said first mentioned condenser for receiving said condensate and bringing it into heat exchanging relation with the boiler feed water at said lower pressure, and means for conveying the condensate from said second condenser to a primary boiler feed heater, said boiler feed waterpassing successively through the primary heater, said second condenser, and said first condenser.

In testimony whereof I aflix my slgnature;

LESLIE EARLISEIBALD. 

